In vehicle washing installations, it is desirable to determine the surface structure of the vehicle to be washed as accurately as possible in order to guide treatment devices such as the rotating brushes of the displaceable washing portal as close as possible to the vehicle surfaces without damaging the vehicle or accessory parts mounted thereon.
In conventional vehicle washing installations, this is usually achieved with light barriers that are arranged on the vehicle washing installation laterally or above the vehicle and determine the vertical contour of the vehicle. For example, DE 32 08 527, DE 35 44 390 or DE 202 04 586 disclose scanning devices that are situated in front of the first work station of the washing installation and consist of several light barriers that are arranged vertically on top of one another or in a matrix-like fashion in order to determine the vertical contour of the vehicle. In the portal washing installation according to DE 38 25 346, a unit for determining the vertical contour is provided which consists of light barriers arranged vertically on top of one another, wherein said unit is arranged directly on the displaceable portal. In addition, a light barrier arrangement is positioned on the vertically displaceable drying nozzle in order to determine and control the distance of the drying nozzle from the vehicle roof.
DE 44 17 864 also discloses a light barrier arrangement that, however, does not determine the vertical contour of the vehicle. In this case, two light barriers are vertically arranged on the sides of the vehicle in order to determine the lateral contour of the vehicle and control the lateral treatment modules accordingly.
The disadvantage of carrying out contour measurements and controlling vehicle washing installations with these known apparatuses is that the vertical contour can only be determined at the respectively highest point and the lateral contour can only be determined at the points of the vehicle that protrude farthest, such that the actual three-dimensional surface structure of the vehicle to be washed cannot be determined.
Another vertical contour measurement is described in DE 44 39 583. In this case, an ultrasonic transmitter/receiver emits an ultrasonic beam toward the vehicle surface in the longitudinal direction during the relative movement between the vehicle and the washing portal, wherein said ultrasonic beam is directly reflected back to the ultrasonic transmitter/receiver at a few locations. The transit time of these more or less randomly reflected beams is determined, and an image of the vertical contour of the vehicle surface is prepared therefrom. The disadvantage of this method is that the vehicle contour can only be determined at a few locations in this case, and it is not possible to easily determine whether the respectively highest locations of the vehicle are contained in this vertical contour.